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Ladan Shams, Robyn Kim; Task-irrelevant sound facilitates visual motion detection. Journal of Vision 2010;10(7):892. doi: 10.1167/10.7.892.
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© ARVO (1962-2015); The Authors (2016-present)
Different sense modalities interact in a variety of perceptual tasks. For example, auditory motion can influence visual motion direction discrimination (Meyer & Wuerger, 2001; Soto-Faraco et al., 2002). Many multisensory integration phenomena have been explained well by interactions at an inference level (e.g., Bayesian or maximum likelihood inference). However, signals of different modalities may also interact at a sensory level. This study tests whether sound can affect perceptual sensitivity to visual motion, aside from any inference or decisional influence. Subjects performed a 2IFC visual coherent motion detection task, in which one interval contained coherent motion in a fixed direction (e.g., 0°), and the other contained random motion. Subjects were asked to detect which interval contained the coherent motion stimulus. In addition to visual trials, our task-irrelevant congruent group experienced audiovisual trials in which sound moved in BOTH intervals, in the same direction as the coherent visual stimulus. Since sound moved identically in both intervals, it provided no indication as to which interval contained the visual coherent motion, and thus was task-irrelevant. Another group received audiovisual trials with task-relevant sound (i.e., moving only in the interval with coherent visual motion), and a third group experienced task-irrelevant incongruent sound (i.e., moving in both intervals but in the opposite direction of visual motion). As expected, subjects performed best when the visual stimulus was accompanied by congruent, task-relevant sound. Surprisingly though, visual motion detection was also significantly enhanced by the task-irrelevant congruent sound. Task-irrelevant sound moving in the opposite direction of visual motion did not yield any benefit, ruling out the possibility that the effect results from general alerting or attentional modulation by sound. These results suggest that auditory motion can facilitate perception of visual motion at a sensory level, independent of its contribution to inference and decision processes.
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